Am new to RPAS Assortment planning application,and I have a query in Assorment planning Maintain Curve Profiles

The percentages which are entered in maintain curve profiles will change in resulting buying periods If the length of the buying period does not match that of the lifecycle curve (with exception to curves 1 and 2), the percentage distribution over weeks is extrapolated and normalized to
100% using the shift and resize logic.

Can anyone explain how this percentage distribution over weeks is extrapolated.Appreciate if any one can give explanation with examples